This invention pertains to a fuel injection apparatus used for a cylinder direct injection two cycle internal combustion engine which is adapted to inject a fuel from an injector directly into a cylinder of the two cycle internal combustion engine and a method of controlling the fuel injection apparatus.
A fuel injection apparatus for a cylinder direct injection two cycle internal combustion engine which is adapted to inject a fuel directly into a cylinder comprises an injector provided so as to inject a fuel into a cylinder ( a combustion chamber) of the engine, a high pressure fuel pump to supply the fuel to a fuel supply port of the injector, a pressure regulator to control a pressure of the fuel (a fuel pressure) applied from the fuel pump to the injector so as to keep it a controlled value, an electronic control unit (ECU) to control the injector, signal generation means to provide a revolution information of the engine, revolution detection means to detect a revolution of the engine, throttle valve opening degree detection means to detect an opening degree of a throttle valve of the engine and various sensors to detect various control conditions including an atmospheric pressure, a cooling water temperature and an intake air temperature which are other than the revolution and the opening degree of the throttle valve and apply them to the ECU.
The ECU comprises a CPU which accomplishes reference injection time arithmetical operation means to arithmetically operate a reference injection time which is to be used for a basis for determining a time during which the fuel is injected from the injector relative to the revolution of the engine and the opening degree of the throttle valve, correction value arithmetical operation means to arithmetically operate correction values by which the reference injection time is to be multiplied in accordance with the respective control conditions detected by the various sensors in order to correct the injection time relative to the control conditions and practical injection time arithmetical operation means to arithmetically operate a practical injection time by multiplying the reference injection time by the thus arithmetically operated corrections value whereby a drive current is supplied to the injector so as to inject the fuel during the thus determined practical injection time.
The ECU also serves to control an ignition system for the internal combustion engine relative to various control conditions such as the revolution of the internal combustion engine and so on.
The injector may be in the form of an electromagnetic fuel injection valve comprising an injector body having a fuel supply port through which the fuel is supplied from the fuel pump and a fuel injection port, a valve to open or close the fuel injection port of the injection body and a solenoid to drive the valve. The injector opens the valve to inject the fuel while a predetermined drive current flows through a coil of the solenoid from the ECU.
In such a fuel injection apparatus as aforementioned, the amount of the fuel to be supplied to the engine is determined by the product of the fuel pressure applied to the injector and the fuel injection time, but since variation in both of the fuel pressure and the fuel injection time makes the control complicated, in general, the fuel pressure applied to the injector when the engine is normally operated is so controlled as to be kept at a desired objective value set within the range of 7 to 9 MPa and the CPU controls only the fuel injection time to thereby control the amount of the fuel to be supplied to the engine.
Also, the ECU controls the injector so as to stop driving the injector to stop the fuel from being supplied when a stop instruction is given, also stop driving the fuel pump and furthermore stop the operation of the ignition system to ignite the engine whereby the engine is stopped.
In the prior art two cycle internal combustion engine having the injector mounted on a throttle body, the injector is disposed in front of the throttle valve so that the fuel is injected from the injector toward a crankcase. The thus injected fuel and air flowing through the throttle body are introduced into the crankcase so that they are combined with each other within the crankcase.
In this two cycle engine, the heat of the crankcase is lost due to evaporation heat generated when the fuel and the air are combined within the crankcase. Furthermore, since the crankcase is cooled by the cooling water circulating through the cooling water passage formed in a housing of the crankcase, the temperature of the crankcase is restrained from rising. In such a two cycle engine as the fuel and the air are combined with each other in the crankcase, the crankcase is kept at a temperature substantially identical to the cooling water temperature due to the evaporation heat of the fuel and the cooling water.
As aforementioned, in case that the fuel and the air are combined with each other in the crankcase, the temperature of the engine is substantially identical to that of the cooling water and therefore the amount of fresh air flowing through the scavenging passage into the combustion chamber can be accurately supposed by estimating an air density of the interior of the crankcase from the atmospheric pressure, the cooling water temperature and the intake air temperature.
Thus, the fuel injection time required for obtaining a mixture gas of appropriate air to fuel ratio can be determined by multiplying the reference injection time determined relative to the revolution of the engine and the throttle valve opening degree by the correction values determined relative to the atmospheric pressure, the cooling water temperature and the intake air temperature. This enables to obtain the combustion state always most suitable for variation in the operation conditions such as the revolution and the loads and the environment conditions such as the atmospheric pressure, the cooling water temperature, the intake air temperature and so on.
On the other hand, in case that the fuel is injected directly into the cylinder, since the fuel is never evaporated in the crankcase and therefore the temperature of the crankcase is never lowered due to the evaporation heat of the fuel, the temperature of the crankcase sometimes gets higher than the cooling water temperature. This sometimes disturbs the amount or density of the air flowing through the scavenging passage into the combustion chamber from being estimated from the atmospheric pressure, the cooling water temperature and the intake air temperature.
Thus, it will be noted that in the cylinder direct injection type two cycle internal combustion engine, the appropriate injection time cannot sometimes be determined only by correcting the injection time relative to the atmospheric pressure, the cooling water temperature and the intake air temperature, and therefore, the appropriate combustion cannot be always made relative to the operation state and the environment conditions.
Accordingly, it is a principal object of the invention to provide a method of controlling a cylinder direct injection type two cylinder internal combustion engine adapted to always make an appropriate combustion in spite of variation in the operation states and the environment conditions.
It is another object of the invention to provide a cylinder direct injection type two cylinder internal combustion engine adapted to always make an appropriate combustion in spite of variation in the operation states and the environment conditions.
In accordance with one aspect of the present invention, there is provided a method of controlling a fuel injection apparatus for a cylinder direct injection type two cycle internal combustion engine comprising the step of arithmetically operating an injection time of the fuel injection apparatus in accordance with various control conditions whereby the fuel injection apparatus is so controlled that a fuel is injected during said injection time determined by said arithmetical operation, the method further comprising the steps of detecting a scavenging temperature of the two cycle internal combustion engine (an air temperature in the scavenging passage) and arithmetically operating the injection time while also using the detected scavenging temperature as another control condition.
Normally, when the injection time should be arithmetically operated, a reference injection time which is used for a basis for determining a time during which the fuel is injected from the fuel injection apparatus is determined by being arithmetically operated relative to a revolution of the internal combustion engine and an opening degree of a throttle valve and an practical injection time is determined by multiplying the reference injection time by correction values which are in turn determined by being arithmetically operated relative to the control conditions such as the atmospheric pressure, the cooling water temperature, the intake air temperature and so on which are other than the revolution of the engine and the opening degree of the throttle valve.
In case that the practical injection time is arithmetically operated by this method, the practical injection time is determined by multiplying the reference injection time by a correction value determined relative to the scavenging temperature as well as the correction values determined relative to the other control conditions.
In accordance with another aspect of the invention, there is provided a fuel injection apparatus for cylinder direct injection two cycle internal combustion engine comprising an injector provided so as to directly inject a fuel into a cylinder of the two cycle internal combustion engine, a fuel pump to supply the fuel to the injector, a pressure regulator to control a fuel pressure applied from the fuel pump to the injector so as to keep it a controlled value, a control unit to control the injector so as to inject the fuel during the injection time determined by being arithmetically operated in accordance with the various control conditions and a scavenging temperature detector to detect a scavenging temperature of the two cycle internal combustion engine, the control unit being so constructed to arithmetically operate the injection time while also using the detected scavenging temperature as another control condition.
In many cases, the control unit of the fuel injection apparatus for cylinder direct injection type two cycle internal combustion engine may have revolution detection means to detect a revolution of the internal combustion engine, throttle opening degree detection means to detect an opening degree of a throttle valve of the internal combustion engine, various sensors to detect various control conditions including at least an atmospheric pressure, a cooling water temperature and ah intake air temperature which are other than the revolution of the engine and the opening degree of the throttle valve, reference injection time arithmetical operation means to arithmetically operate a reference injection time which is to be used for a basis for determining a time during which a fuel is injected from the injector relative to the revolution of the engine and the opening degree of the throttle valve, correction value arithmetical operation means to arithmetically operate correction values by which the reference injection time is to be multiplied in accordance with the respective control conditions detected by the various sensors in order to correct the injection time relative to the control conditions and practical injection time arithmetical operation means to arithmetically operate a practical injection time by multiplying the reference injection time by the correction value arithmetically operated by the correction values arithmetical operation in accordance with the control conditions whereby the injector is so controlled as to inject the fuel during the thus determined practical injection time.
In such a fuel injection apparatus to which the invention should be applied, a scavenging temperature detector may be provided to detect a scavenging temperature of the two cycle internal combustion engine and the correction value arithmetical operation means is so constructed as to arithmetically operate the injection time while also using the detected scavenging temperature as additional control condition.
With the injection time adapted to be corrected additionally in accordance with the scavenging temperature detected by the scavenging temperature detector, since the density or amount of the air supplied through the scavenging passage into the combustion chamber can be accurately estimated, the injection time or the amount of fuel injection required for obtaining the mixture gas of proper air to fuel ratio within the combustion chamber can be accurately determined.
Thus, according to the invention, the mixture gas of proper air to fuel ratio in accordance with variation in the operation states and the environment conditions can be always obtained and therefore an appropriate combustion can be accomplished, which causes the property of the engine to be improved.
The scavenging temperature detector may preferably comprises a temperature sensor provided so as to detect a temperature in a scavenging passage of the two cycle internal combustion engine at a position closer to a crankcase.